Battery charging system



Feb. 28, 1950 J. H. LITTLE ETAL 2,498,814

BATTERY CHARGING SYSTEM Original Filed NOV. 2, 1943 REGULA TOR AND y- CUTOUT RELAY INVENTORS JOHN H. LITTLE m v BY WILLIAM J. RAvY M THEIR A TTORNEYS latented Feb. 28, 1950 BATTERY CHARGING SYSTEM John H. Little, Huntington Woods, Mich., and William J. Rady, Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Original application November 2, 1943, Serial No. 508,694. Divided and this application March 6, 1947, Serial No. 732,710

This invention relates to battery charging systems.

This application is a division of our copending application Serial No. 508,694, filed November 2, 1943, and issued December 2, 1947, Patent Number 2,431,945.

An aim of the present invention is to protect the battery from excessive decomposition of the water in the electrolyte, particularly when the battery is substantially fully charged and warm. This aim is accomplished by providing means controlled by battery temperature and charging generator voltage for increasing the resistance of the charging circuit to reduce the amount of current flowing to the battery. A resistance element in the charging circuit is normally bypassed by a relay whose magnet coil is controlled hy a thermal switch in the battery and by a relay whose magnet coil is connected with generator terminals.

A further aim of the present invention is to provide a battery that is especially designed so that it is feasible to assemble the thermal switch from the exterior of the battery and below the normal level of the electrolyte and still not have the switch come in contact with the electrolyte, hut also protect it from fumes caused by a too h gh rate charge, with the result that the corrosive liquid and fumes are excluded from the metal parts of the switch.

Still another aim of the invention is the provision of a special enclosure for the thermal switch, which enclosure has a heat conducting wall immersed in a controlling electrolyte so as to effect a uniform operation of the thermal switch irrespective of the electrolyte level deviation from the normal level. This is accomplished by providing the battery case with a recess adapted to receive a cup-shaped cover with the thermal switch mounted thereon, said cup-shaped cover being fitted with the recess when the cover is inverted and positioned within the recess, said cover forming double thickness walls within the walls of the recess so that the only single thickness wall is the bottom wall of the recess.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a, preferred embodiment of the invention is clearly shown.

In the drawings:

Fig. 1 is a wiring diagramof battery charging system embodying the present invention.

Fig. 2 is a longitudinal sectional view of a thermal switch located in a battery cell cover.

3 Claims. (Cl. 320'23) Fig. 3 is a view of the thermal switch looking in the direction of arrow 3 of Fig. 2.

Referring to Figs. 2 and 3, a battery cell cover I!) provides a hollow member H depending from the cover. This member comprises a skirt closed by a wall l2 and which constitutes a recess or well l3 for housing a thermal switch I4. The bottom wall which closes the skirt depends a substantial distance below the cover in so that it will be immersed in the electrolyte. The normal level of electrolyte in the cell is indicated by the line IS. The thermal switch it, as shown in the drawing, comprises a cup-shaped case or cap l6 having a stud or post 11 to which one end of a spiral bimetal element I8 is attached. The element l8 carries a contact 19 for engaging a contact 20, mounted on an ear 2| of a bracket 22 adjustable in an arcuate slot 23, concentric with the center of the stud IT. The bracket 22 has an arcuate slot 23 for receiving a screw 25, threaded into an insert 26 in the case iii. The screw 25, when threaded home in the insert 26, holds the bracket in the position necessary to provide a certain initial gap between the contacts I9 and 20. The length of the gap will determine the degree of temperature to which the battery will attain when the contacts close. When this gap is greater, the temperature will be higher and vice versa. The thermal switch i4 is readily affected by changes in battery cell temperature.

The thermal switch 18, including the cupshaped case 16 of insulating material, has the same outside diameter as the recess 13 so that the rim will fit snugly with the internal surfaces of the recess performing a substantial hermetic seal therewith. In the present instance, the case includes an annular rim or flange 30, the ends of which, rest upon the bottom wall 12. In this arrangement, the flange 30 and the skirt i i form a double thickness wall with the result that fumes which surround the case M, while in use, are substantially eliminated from the metal parts within the case 16. It will be noted, that the lowermost edges of the spiral bimetal strip I8 are adjacent the bottom wall i2, which is a single thickness wall so as to effect a uniform operation of the thermostatic switch irrespective of the electrolyte level deviation from the normal level indicated by the line I5.

At the time of forming the cap, it is formed with suitable apertures to receive the reduced end of the post I! and the insert 26 and the recess 23 to receive the bracket 22. The post I! and insert 26 protrude through the wall as shown in Fig. 2 to make provisions for external connections with insulated conductors 32 and 33 respectively. The external connections are covered with an insulating material 34. The cap is fitted into the recess and is maintained in sealed or fluidtight relation by additional insuiating ma= terial 35 applied over the top of the material 96. It is to be understood, the material could be a preformed plate with suitable apertures through which the conductors 32 and 33 are threaded.

With a thermostatic switch so constructed as sealed as hereinabove set forth, which is shown in Fig. 2, it will be appreciated that the thermostatic switch is enclosed within a chamber 37 that is completely isolated from electrolyte, fumes and other outside foreign matter which may cause corrosion of the metal elements of the thermostatic switch. Due to the character or the assembly, the thermostatic switch E4, the switch is positioned adjacent the one thickness wall 42 which is normally immersed in the electrolyte so that irrespective of the deviations in the electrolyte level, the operation of thermostatic switch I4 is uniform, in that the heat passing through the wall l2 into the chamber 31 is somewhat localized in raising the temperature within the chamber.

In accordance with the present invention, provision is made for the control of current to the battery by heat generated in the battery. This is illustrated diagrammatically in Fig. 1. As shown, a generator 40, is connected through a voltage regulator and cutout relay unit 4!, an ammeter 42 and a resistance 43 with a battery 44, a cell of which carries the thermal switch M. The contacts 45 and 46 of a relay 41 normally shunt the resistance '43 as indicated by the heavy lines connecting, the generator 49 and battery 44. The magnet coil 48 of relay 4'! is energized by current from the generator 40 when contacts l9 and 20 of thermal switch M are engaged concurrently with the engagement of normally open contacts 49 and 50 of a relay i whose magnet coil 52 is connected across the generator armature 53.

When the battery 44 is substantially fully charged, the generator voltage is sufiicient to cause an armature 55 of the relay 51 to move down to close contacts 49 and 50. This alone will not cause the magnet coil 48 of relay 47 to be energized. If when the contacts 49 and 50 of relay 5| are closed, the contacts [9 and of thermal switch l4 close due to an elevated battery temperature, so if when the contacts 19 and 29 of switch l4 are closed, the contacts 49 and 59 of relay 5| close due to an elevated generator voltage, the magnet winding 48 of relay 41' is energized to pull the relay armature 89 down to separate contacts 45, 46 thereby interrupting the,

shunt circuit of resistance 43 and rendering said resistance effective, as indicated by heavy broken lines in Fig. 1, to decrease the flow of current to the battery 44 to protect it from overheating.

The load of lamps 6| of other current consuming devices connected with ammeter 42 by switch 62 is not affected by the reduction in battery charging current.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a battery charging system having a thermal control device for protecting the battery electrolyte from excessive decomposition of water due to excessive heat when the battery is fully charged and warm, comprising in combination; a battery case containing a quantity of electrolyte; a cover for the case and including a well having a bottom wall adapted to be immersed in the electrolyte; a closure for the well; a battery cir cult including a normally open thermostatic switch carried by the closure and disposed adjacent the bottom wall of the well and subjected to the high internal temperature of the battery to close the switch to complete the circuit to reduce the amount of current through the battery, said closure having a depending skirt formed to fit the interior of the well and provide a double thickness side wall above the bottom wall whereby accurate temperature control of the electrolyte is obtained; and means for securing the closure to the cover and sealing the juncture between the closure and case.

2. In a battery charging system having a thermal control device for use in combination with a battery case comprising, a battery cover made of nonconducting material for closing the case and including a closed end tubular skirt depending from the case with the closed end immersed in electrolyte within the case; a cup-shaped mem-- ber inserted within the tubular portion and having its closed end spaced from the closed end of the tubular portion to form a chamber and having its annular wall forming a double thickness wall with the tubular wall of the skirt and cause heat within the case to localize and pass through the closed end of the skirt into the chamber; and a battery circuit including a normally open thermostatic switch supported within the chamber, said switch being moved to a closed position when the temperature within the chamber reaches a predetermined value to close a circuit so as to reduce the amount of current passing through the battery.

3. In a battery charging system having a thermal control device for protecting the battery electrolyte from excessive decomposition of water due to excessive heat when the battery is fully charged or warm, comprising in combination; a

battery case containing a quantity of electrolyte; a cover for the case including an enclosure depending therefrom, said enclosure including a thick wall portion and a thin wall portion, said thin wall portion adapted to be immersed to cause heat within the case to localize and pass through the thin wall portion; a battery circuit including a normally open thermostatic switch supported within the enclosure and located adjacent the thin wall portion and responsive to battery temperature for closing and opening said circuit, said switch when closed reducing the amount of current through the battery.

JOHN H. LITTLE.

WILLIAM J. RADY.

REFERENCES CITED The following references are of record in the file of this patent:

I UNITED STATES PATENTS Number Name Date 991,112 Turbayne May 2, 1911 1,976,404 Leingang Oct. 9, 1934 2,022,874 West Dec. 3, 1935 2,354,877 Peters Aug. 1, 1944 2,355,488 Van Vulpen et al. Aug. 8, 1944 2,369,826 Heyer et a1 Feb. 20, 1945 2,421,523 Rady June 3, 1947 2,427,729 Jenkins Sept. 23, 1947 2,431,945 Little et al. Dec. 3, 1947 

